HF Vapor Etcher – SPTS Monarch3

The SPTS Monarch3 is a vapor phase HF silicon dioxide etcher.

This tool allows isotropic etching of silicon dioxide, specifically designed for MEMS release by etching of sacrificial oxide.
The etch happens in a controlled environment, where temperature, pressure and flows of alcohol catalyst, HF and nitrogen gas flows can be adjusted to tune the etch process and prevent stitching of suspended structures and devices.

The tool comes with a manual, tripe wafer loadlock for ease of use in a research environment. It can host 200mm wafers down to small chips.

To fabricate mobile Silicon MEMS devices on SOI platform, one needs to selectively remove the sacrificial oxide below the active structures.
While using HF in aqueous solution, the process of post-etch drying is a very critical part: in fact droplets of liquid below the released structures can apply strong capillary forces to the released parts, free to move because the HF has removed the anchoring oxide underneath, leading to detrimental collapse of such structures to the substrate and therefore device failure.
For this reason the release process is better performed in the gas/vapor phase, where no liquid forms below suspended structures and water rinsing is not needed.

The Monarch3 tool etches sacrificial silicon dioxide by flowing HF gas into a reaction chamber along with ethanol, used to catalyze the etch reaction. The reaction takes place at controlled pressure and temperature, so that the water produced in the etch reaction will not form liquid droplets nor drive the reaction faster (water acts as a catalyst for the etching reaction too). Therefore all sacrificial oxide can be etched in a controlled way, avoiding liquid droplet formation that may cause structure collapse on the wafer.

Supported Sample Sizes:

• Maximum wafer diameter: 200 mm (8 in).
• Maximum number of wafers per run: 3
• Small pieces supported: Yes
• Smaller wafer sizes: Yes

Typical Applications:

• Silicon oxide etching
• MEMS device release
• Compatible with Al-based metallization

Tool access:

• Operated by trained STAFF members only
• Process on your devices to be discussed with tool manager